If you haven't seen any of XRP's "Seeds" range, download the free Fantasy Seeds PDF, as they all follow the same format. The ZIP file includes both Print & Screen versions of the PDF.
These are exactly what the name suggests - barebones adventure seeds for GMs to build upon. They range from simple one liners "The PCs are car-jacked", to quite detailed and convoluted plots, but they almost all leave the ultimate resolutions to the GM.

These are designed for the modern day real world, for the main part without any "kewl powerz", but the ideas could easily be adapted to most other genres/subgenres.